CMOS Image Sensor Pixel Electrical Barrier Height Optimization

Solution Overview

Problem

In solid-state imaging apparatuses, the blooming phenomenon occurs due to high sensitivity pixels being saturated earlier, leading to coloration and degradation of image quality, especially when using white pixels in addition to RGB pixels, as they overflow electric charges to adjacent pixels, disrupting linearity and white balance.

Innovation Solution

The apparatus employs a pixel array configuration where the first pixel (corresponding to color components) and second pixel (with higher sensitivity) have different electrical barriers, allowing for controlled discharge of unnecessary electric charges, with the second pixel's barrier being deeper to prevent saturation and overflow, thereby suppressing the blooming phenomenon.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If high sensitivity pixels (W pixels) are used in addition to RGB pixels, then image brightness in dark places is improved, but blooming phenomenon occurs causing coloration and image quality degradation

Engineering Contradiction:

Improveimage brightnessVSAvoidimage quality

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The pixel array is segmented into different types of pixels (first pixels with color components and second pixels with higher sensitivity) that have different electrical barrier heights. This segmentation allows each pixel type to be optimized for its specific function while preventing cross-contamination of electric charges between pixels.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different pixels are given different local properties through varying electrical barrier heights. Second pixels (high sensitivity pixels) have deeper electrical barriers compared to first pixels, creating local quality differences that prevent saturation and blooming in high sensitivity pixels while maintaining their enhanced light capture capability.

Inventive Principle:

Principle #3Local quality

2Measurement precision

If second pixels with higher sensitivity are used, then sensitivity to incident light is improved, but electric charges saturate earlier causing overflow to adjacent pixels

Engineering Contradiction:

Improvesensitivity to incident lightVSAvoidelectric charge overflow

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The electrical barrier height parameter is changed for different pixel types. Second pixels are configured with deeper electrical barriers (higher potential walls) compared to first pixels, which prevents electric charge saturation and overflow while maintaining high sensitivity to incident light through optimized photoelectric conversion units.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If all pixels have the same electrical barrier height, then manufacturing is simplified, but coloration occurs due to blooming phenomenon in high sensitivity pixels

Engineering Contradiction:

Improvepixel array fabricationVSAvoidcolor accuracy

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

Different pixels are given different local properties through varying electrical barrier heights. Second pixels (high sensitivity pixels) have deeper electrical barriers compared to first pixels, creating local quality differences that prevent saturation and blooming in high sensitivity pixels while maintaining their enhanced light capture capability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The pixel array is segmented into different types of pixels (first pixels with color components and second pixels with higher sensitivity) that have different electrical barrier heights. This segmentation allows each pixel type to be optimized for its specific function while preventing cross-contamination of electric charges between pixels.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration improves coloration and image quality by maintaining linearity across all pixels, preventing coloration and degradation, even in low-light conditions, by ensuring that electric charges are properly managed and do not overflow, thus enhancing the overall image quality.

Implementation Method 1

a first photoelectric conversion unit that generates electric charges according to an amount of incident light

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS10431622B2Solid-state imaging apparatus, and electronic apparatus

Publication Date: 2019.10.01 SONY SEMICON SOLUTIONS CORP

AI summary

The present technology relates to a solid-state imaging apparatus and an electronic apparatus that makes it possible to improve coloration and improve image quality. The solid-state imaging apparatus is formed so that, in a pixel array unit in which combinations of a first pixel corresponding to a color component of a plurality of color components and a second pixel having higher sensitivity to incident light as compared with the first pixel are two-dimensionally arrayed, a first electrical barrier formed between a first photoelectric conversion unit and a first unnecessary electric charge drain unit in the first pixel, and a second electrical barrier formed between a second photoelectric conversion unit and a second unnecessary electric charge drain unit in the second pixel have different heights, respectively. The present technology can be applied to, for example, a CMOS image sensor.